[asimplelife]

Just a bit of an update if it's any use.
I had this leak so tried the supercheap o-ring pack which weren't really the right size for the small but I used the closest and nothing for the large so reused the existing with sealant.
However I think it's still leaking (although it may still be oil coming out of my degreased alternator)?
So rang Ford spares today to get the genuine o-rings.
V890156Sis now obsolete - this was the small one? (if so I will try again with a generic size).
V890066S is still available for $6.15 - this is the large one? (if it is and if it resolves my leak I might order a couple of spares).

A couple of other suggestions from other threads I'll just list anyway;
"i also added some ultra grey around the seal for added leak prevention."
"you can swap the larger o-ring for an alloy sump plug washer, tends to work a lot better"